Middle Eocene-Early Miocene Dasypodidae (Xenarthra) of Southern South America, successive faunas in Gran Barranca; Biostratigraphy and Palaeoecology.

CARLINI, A. A.,; CIANCIO MR.; SCILLATO-YANÉ GJ

In: The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic of Patagonia”, Madden, R.H., Carlini, A.A., Vucetich, M.g. and Kay R.F. (eds).

Cambridge University Press

Lugar: cambridge; Año: 2010; p. 106 - 129

Most biostratigraphic sequences in Patagonia and elsewhere in South America have been based on the evolutionary stage and taxonomic representation of “ungulates” (archaic endemic herbivores or southern ungulates) and/or marsupials. Recent collections of microfossils made at Gran Barranca, Patagonia, allow us to assess critically the value of Cingulata (mainly the Dasypodidae) and cingulate assemblages in mammalian biostratigraphy. The numerous and rich fossil localities and levels at Gran Barranca provide the most stratigraphically complete sampling of Cingulata available anywhere in South America. Starting with the “Barrancan” (Eocene) level at the base of the sequence and ending with the “Pansantacrucian” (Miocene) beds at the top of the Sarmiento Formation, dasypodid assemblages demonstrate a very close relationship with sea-surface temperature variation through the late Paleogene. We have studied seven successive faunas with a very rich dasypodid record. While the astegotheriine Dasypodinae decrease in diversity through the late Paleocene – late Eocene interval, the stegotheriine Dasypodinae, and especially the Euphractinae, increase in diversity through the middle Eocene and into the early Oligocene, until euphractines became dominant in the late Eocene. Cingulate assemblages permit speculation that between the upper Casamayoran (Cifelli’s “Barrancan”, around 39–41.6 Ma) and the typical Mustersan (about 38.7 to 37.0 Ma) a distinct faunal assemblage may represent a new subdivision of the mammalian sequence in Patagonia.